Computer-assisted, stereotactic systems, which work with the aid of body structure data obtained from tomographic detection systems and with the assistance of x-ray images produced in situ are known, for example, from U.S. Pat. Nos. 4,791,934 and 5,799,055. X-ray imaging used to assist in operations is discussed in U.S. Pat. Nos. 5,967,982, 5,772,594 and 5,784,431.
Referencing the current position of the structures to be operated on by means of pre-operatively produced three-dimensional patient data and x-ray images produced in situ (fluoro-CT matching) is introduced here as a non-contact method, which is therefore suitable for minimally invasive surgery.
Where accurate medical navigation is to be provided, the prior art still works with the aid of body structure data originating from tomographic detection systems, such as, for example, computer tomography devices or nuclear spin tomography devices. The patient to be treated is thus positionally registered in situ with respect to the image data determined beforehand. Operating instruments are then virtually displayed in the same relation to the image data as to the actual patient, to make the body structure data or, if possible, also x-ray image data useful to the surgeon in the operating room.
Disadvantages of such methods, in which tomographs (CT, MR) or x-ray images are produced, especially for navigating within the framework of treatment, include the radiation load on the patient and the high costs, since such devices are very expensive both to purchase and to maintain and operate.
Attempts have been made to develop systems that may be employed without body structure data separately detected beforehand, for example, based on statistical models of image data sets for body structures. However, such systems lack the required accuracy for the respective patient to be treated.
DE 100 37 491 A1 and WO 99/59106 describe methods for providing 3D information with the aid of fluoro-images. The starting point in all methods is recording transillumination images of the patient or of the desired structure. A localization system is used to obtain spatial information using the images. DE 100 37 491 A1 initially uses two fluoro-images, from which to reconstruct a rough 3D model. Other images from different angles are used to specify the model more precisely. In accordance with WO 99/59106, at least three fluoro-images of the patient are generally made. These are anterior-posterior, lateral and anterior-posterior with the head inclined backwards. In addition to the transillumination images, photographs of the patient are also used. In this prior art, the model is painstakingly adapted in three-dimensional space.